Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D7/00—Producing flat articles, e.g. films or sheets
  • B29D7/01—Films or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/78—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling
  • B29C48/86—Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling at the nozzle zone
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
  • B29C48/10—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels flexible, e.g. blown foils
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/30—Extrusion nozzles or dies
  • B29C48/32—Extrusion nozzles or dies with annular openings, e.g. for forming tubular articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/001—Combinations of extrusion moulding with other shaping operations
  • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/001—Combinations of extrusion moulding with other shaping operations
  • B29C48/0019—Combinations of extrusion moulding with other shaping operations combined with shaping by flattening, folding or bending
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
  • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
  • B29C48/21—Articles comprising two or more components, e.g. co-extruded layers the components being layers the layers being joined at their surfaces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2023/00—Tubular articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2023/00—Tubular articles
  • B29L2023/003—Tubular articles having irregular or rough surfaces

Definitions

• the invention relates to a process for the preparation of blown film from a polymer composition on the basis of polyethylene, which polyethylene has a density of 910 to 940 kg/m 3 , in which the polymer composition is, in molten condition, forced via an extruder through an annular die having a width of at least 1 mm and is made to balloon out by means of a gas, supplied through an opening within the annular die, following which the polymer composition that has formed the balloon is cooled, flattened and rolled up.
• Low-density polyethylene (LDPE) blown film has found large- scale application as packaging material.
• the main requirements to be met by packaging material concern mechanical properties, such as stiffness, tear resistance, tensile strength, puncture resistance, and the like.
• said material must often also satisfy requirements in the field of optical properties such as transparency, opacity and gloss.
• Film to be processed into refuse bags will need to have a good puncture resistance and tear properties, while film for carrier bags must in addition have high stiffness. In applications such as bread packaging, it is especially stiffness and opticals that play a part.
• a method for processing linear polyethylene into blown film using die gaps of about 0,4-5 mm is described in European patent application 51358. This method uses specially formed die gaps in order to prevent melt fracture. The temperature of the melt is between about 162 and 260 °C. This method relates only to linear polyethylene.
• the object of the present invention is to provide a process for the preparation of blown film from a polymer composition on the basis of polyethylene with a density of 910-940 kg/m 3 that is suitable for both linear and non-linear LDPE and that yields a film having good mechanical properties, notably high stiffness and good tear properties.
• This object is achieved by processing the polymer composition in molten condition via an extruder through an annular die having a width of at least 1 mm, at a melt temperature at the location of the die gap of below 160 °C.
• Polymer compositions that are suitable for being processed into blown film in accordance with the invention generally contain at least 50 wt. % polyethylene homopolymer and/or one or more copolymers with a density of 910-940 kg/m 3 .
• Low-density polyethylene homopolymer, copolymers of ethylene with one or more C 3 -C 15 alkenes, copolymers of ethylene and one or more polar comonomers with a comonomer content of at most 10 wt. %, relative to the ethylene (e.g. vinylacetate, methacrylate) can be applied with good results.
• mixtures are suitable, like for instance mixtures of polyethylene homo-and/or copolymers with a density of 910-940 kg/m 3 , or mixtures of polyethylene homo- and/or copolymers having a density of 910-940 kg/m 3 with low-density polyethylene copolymers (with a density less than 940 kg/m 3 ), high density polyethylene (with a density in excess of 940 ⁇ kg/m 3 ) and/or polypropylene.
• these mixtures preferably at least 70 wt %, relative to the total polymer content, of the homo- and/or copolymer with a density of 910-940 kg/m 3 is present.
• the use of a polymer composition on the basis of polyethylene homopolymer or a copolymer of ethylene and one or more polar comonomers with a comonomer content of at most 10 wt. % relative to the ethylene is to be recommended.
• the process according to the invention is particularly suitable for the preparation of films having good mechanical and optical properties from low-density polyethylene homopolymer or ethylene vinylacetate copolymer.
• additives such as stabilisers, slip agents, fillers, colourants, waxes and the like, may be present.
• the amount by weight of additives usually will not exceed 20 % of the amount by weight of polymer.
• the melt index of these polymer compositions may have the usual values, for instance between 0.3 and 30 dg/min. In view of the low processing temperature, however, it is to be recommended to choose a melt index of not lower than 2 dg/min.
• the advantage of the invention is that also polymer compositions having a relatively high melt index can be processed into blown film with good mechanical properties.
• packaging film must not only satisfy requirements with respect of its mechanical properties, but also requirements relating to its optical properties.
• the optical properties of the film improve when use is made of a polymer composition having a melt index of at least 5 dg/min, in particular at least 8 dg/min.
• the polymer composition exits the annular die in molten condition and is subsequently blown up.
• the resulting balloon is cooled by contacting it with relatively cool air or water.
• Balloon diameter divided by annular die diameter is called the blow-up ratio. This may vary between 1 and 6, but generally is 1.5 to 4. These values can also be applied in the process according to the invention, yielding good results.
• the process according to the invention is suitable especially for the preparation of monolayer film, but can also be used for multilayer film.
• Blown film was prepared under conditions as shown in the table. Use was made of a Schwabenthan extrusion equipment with a screw diameter of 30 mm and a length/diameter ratio of 24 : 1. The diameter of the annular die was 5 cm.
• the melt temperature at the die gap was determined by infrared measurement. Of the film, the following properties were determined:

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
• Polymerisation Methods In General (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
• Wire Bonding (AREA)
• Piezo-Electric Transducers For Audible Bands (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Orthopedics, Nursing, And Contraception (AREA)
• Materials For Medical Uses (AREA)
• Medical Preparation Storing Or Oral Administration Devices (AREA)
• Medicinal Preparation (AREA)
• Document Processing Apparatus (AREA)
• Display Devices Of Pinball Game Machines (AREA)
• Television Systems (AREA)
• Slot Machines And Peripheral Devices (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=19843445

Family Applications (1)

Country Status (14)

Cited By (2)

Families Citing this family (3)

Citations (4)

Family Cites Families (5)

• 1984
  • 1984-02-07 NL NL8400375A patent/NL8400375A/nl not_active Application Discontinuation
• 1985
  • 1985-02-05 KR KR1019850000717A patent/KR850005789A/ko not_active Withdrawn
  • 1985-02-05 NZ NZ211055A patent/NZ211055A/en unknown
  • 1985-02-05 CA CA000473555A patent/CA1253307A/en not_active Expired
  • 1985-02-06 FI FI850500A patent/FI88127C/fi not_active IP Right Cessation
  • 1985-02-06 AT AT85101240T patent/ATE46650T1/de not_active IP Right Cessation
  • 1985-02-06 EP EP85101240A patent/EP0152865B1/de not_active Expired
  • 1985-02-06 ES ES540166A patent/ES8606424A1/es not_active Expired
  • 1985-02-06 JP JP60020200A patent/JPH069863B2/ja not_active Expired - Lifetime
  • 1985-02-06 NO NO850452A patent/NO171255C/no unknown
  • 1985-02-06 DE DE8585101240T patent/DE3573228D1/de not_active Expired
  • 1985-02-07 AU AU38518/85A patent/AU570533B2/en not_active Ceased
  • 1985-02-07 DK DK056685A patent/DK162633C/da not_active IP Right Cessation
  • 1985-02-07 TR TR5791A patent/TR22511A/xx unknown

Patent Citations (4)

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